This multicenter prospective controlled clinical trial will evaluate the emergency department (ED) use of Tc99m-sestamibi scanning to aid ED triage of patients presenting with symptoms suggestive of acute cardiac ischemia (ACI) who have normal or non-diagnostic electrocardiograms (ECGs). The trial's primary aim will be to assess the impact of sestamibi scanning on ED triage decisions: the degree to which those ED patients with ACI are hospitalized and those without ACI are not hospitalized.